Thoughts on the evolution of wireless networks and mobile web 2.0

May 09, 2012

LTE to the Plane

Last year I was by chance on one of those Lufthansa planes that had Internet via satellite connectivity when flying back from the US over Europe. Despite the long round trip times, the overall experience was quite breathtaking. The only thing that can be done to reduce the long round trip delay times is not to use a satellite based but a ground based system. This is a bit difficult over the Atlantic but when flying over land, such a system is quite feasible.

While there are perhaps already existing solutions for ground based Internet solutions for planes, another alternative has been trialled recently: LTE to planes. According to this post and an even more detailed post here (sorry, both in German), Airbus, Alcatel-Lucent and Deutsche Telekom "flew" a trial in November 2011to see how well data could be exchanged between a plane and LTE base stations on the ground, separated around 100 km from each other. The post says that standard LTE equipment was used with antennas only slightly modified to direct the signal towards the the sky instead of to the ground. Speeds of 30 Mbit/s were reached in one direction and 17 Mbit/s in the other. The post is a bit ambiguous in which direction which speed was received but nevertheless that is quite impressive and shows that a cell should have more than enough capacity for the few planes that are its coverage area. At such a distance, the article says, 600 base stations would be required to cover Europe. That is just a handful per country.

But don't get your hopes up to see this in planes anytime soon, though, as there is not even yet a frequency band dedicated for this service.

P.S.: And I really wonder where the antenna was installed on the plane? :-)

7 Comments

There is plenty of air-to-ground spectrum available in Europe. One target band for commercial broadband in planes will be in the 5GHz band. But systems won't be COTS LTE - there are some tweaks needed for doppler correction and obviously the airborne systems have some special EMC requirements. Antennas are nowadays typically built into the bottom of the plane right behind the pilots cabin. It is more than one antenna behind a single radome.

I wonder how they did bridge a distance of 100km by standard LTE on 2.6 GHz. Did they use tracking directional antennas? I doubt you can cover a significant angle of airspace in a 100km-radius (i.e. using a wide angle sector antenna) based on standard TX power levels.

In any case it will take years until there's Europe-wide coverage as there are just too many regulatory bodies involved.

Another approach would be to deploy MEO satellites which could significantly reduce latency and provide worldwide coverage, however at significantly higher costs than a ground-based system.